The El Nino weather pattern occurs when weakening trade winds allow warm water in the western Pacific to pulse to the east.
It usually occurs around December every 3-6 years.
Global warming and sunspot activity have been linked to El Nino.
El Nino causes reversals of normal weather patterns worldwide, resulting in drought in usually wet locales and flooding in arid areas.
Trade winds may reverse direction.
Days may lengthen because of Earth's rotation.
Increased precipitation from El Nino brings upsurges in diseases such as cholera, malaria, dengue fever, and Rift Valley fever.
El Nino helped make 1998 the hottest year on record.
Its effects on mortality and the economy are mixed.
El Nino may lessen global warming by temporarily stemming the release of carbon dioxide from the Pacific.
La Nina alternates with El Nino and is fueled by abnormally cold water in the eastern Pacific.
It typically lasts a year.
La Nina reverses El Nino's effects but also brings drought to some parts of the planet while drenching others.
It is associated with colder temperatures on the US West Coast.
Predicting El Nino and its behavior is aided by computer modeling, a detection system that monitors Pacific winds and waves through 70 stations floating on buoys, and weather satellites that detect ocean warming.
Private forecasting companies who sell predictions to businesses are pushing forecasting frontiers.
Forecasting El Nino behavior allows farmers to vary sowing and planting periods and vaccinate livestock, and mosquito habitats to be treated with insecticides.
